Studies of Magnetic Substrates for SP-STM

Spin-polarized scanning tunneling microscopy (SP-STM) is a technique that combines atomic scale spatial resolution with magnetic sensitivity. To perform detailed measurements of novel spin systems, it is necessary to accurately characterize the magnetization and typical behavior of different spin-polarized tips using a well-known magnetic substrate. Here, we present our work on Cr(001), where alternating terraces are antiferromagnetically coupled, and Fe/Ir(111) which hosts a variety of magnetic orderings depending on film thickness in the few layer regime. For Cr(001), a 1200° C flash anneal results in the appearance of a complex surface reconstruction, island formations, and self-assembled Cr nanowires. Tunneling spectroscopy of these features typically display Kondo-like resonances that may reflect spin-screening or spin-polarized surface states. In preliminary work on Fe/Ir(111), we find the surface is partially covered by monolayer films and bilayer islands. Resolving magnetic contrast in these films will allow us to precisely characterize the magnetization of our tips in three spatial dimensions, which can then be used to study and map spin in other systems.